KR20120046053A - Method for producing polarizing plate - Google Patents

Abstract

PURPOSE: A method for manufacturing a polarizing plate is provided to manufacture the polarizing plate in which optical property and junction strength are excellent by controlling excessive reverse curl. CONSTITUTION: A polarizing film(21) is returned in order to be inserted between an acrylic resin film(25) and a transparent resin film by a material film returning process. The acrylic resin film is attached to one side of the polarizing film by using adhesive of hardening property. The transparent resin film is attached to the other side of the polarizing film by using the adhesive of hardening property. A first junction roll(15) contacts to the acrylic resin film and revolves to a returning direction of the acrylic resin film. A second junction roll(16) contacts to the transparent resin film and revolves to a returning direction of the transparent resin film. The adhesive is hardened.

Description

Manufacturing method of polarizing plate {METHOD FOR PRODUCING POLARIZING PLATE}

This invention relates to the manufacturing method of a polarizing plate, and especially relates to the manufacturing method of the polarizing plate in which the acrylic resin film was bonded by the single side | surface of a polarizing film, and the transparent resin film was bonded by the other surface of the polarizing film.

The polarizing plate is used as a structural member of a liquid crystal display device, and the demand is rapidly increasing with the spread of a liquid crystal display device. And with the application to the large-sized television etc. of a liquid crystal display device, the polarizing plate is also required to further reduce thickness and cost, while maintaining or improving the performance.

In general, the polarizing plate has a structure in which a transparent protective film is bonded to at least one side, usually both sides, of a polarizing film made of a polyvinyl alcohol-based resin in which a dichroic dye is adsorbed and oriented. The film of cellulose acetate type resin represented by triacetyl cellulose is used for the protective film of a polarizing plate, and the thickness is about 40-120 micrometers normally. The adhesive which consists of aqueous solution of polyvinyl alcohol-type resin is used for bonding to such a cellulose acetate type resin film to the polarizing film in many cases. However, the polarizing plate which laminated | stacked the protective film on the polarizing film via water-soluble adhesive had a problem that a polarizing performance fell or peeled from a polarizing film when it used for a long time under moist heat conditions.

Then, there exists an attempt to comprise at least one of the protective films joined to both surfaces of a polarizing film by resin other than cellulose acetate type resin. As such resin, a technique using acrylic resin which is a relatively inexpensive resin material is known. For example, the protective film (refer Unexamined-Japanese-Patent No. 2009-122663) using the (meth) acrylic-type resin containing a lactone ring is known. Moreover, the protective film (refer Japanese Unexamined-Japanese-Patent No. 2008-216586) which uniaxially or biaxially stretched acrylic resin in the range of 50-200% of draw ratio is also developed. By using such stretched acrylic resin, it can be set as the optical film excellent in mechanical strength and heat shrinkability.

The polarizing plate in which the elongate protective film was laminated | stacked on the elongate polarizing film can be manufactured by the roll-to-roll bonding method using a bonding roll. A roll-to-roll bonding system is a method of laminating | stacking a long protective film on a long polarizing film via an adhesive agent, and bonding a polarizing film and a protective film by pinching with two bonding rolls in this state. In this bonding method, the adhesive agent hardened | cured by an active energy ray etc. is used in many cases. Such a curable adhesive is preferable because the curing rate is high and the adverse effects due to moisture are hardly exerted on the film.

MEANS TO SOLVE THE PROBLEM The present inventors provide the method of manufacturing the polarizing plate provided with the acrylic resin film in the single side | surface of a polarizing film, and the transparent resin film in the other side by a roll-to-roll bonding method for the purpose of further aiming at the cost reduction and thickness reduction of a polarizing plate. Reviewed. As a result, when roll-to-roll bonding is performed on normal conditions, the acrylic resin film side will become convex by the difference of the shrinkage stress of an acrylic resin film and a transparent resin film, and a transparent resin film side or the surface will be carried out. It was found that there was a tendency to exhibit a so-called inverse curl in which the formed pressure-sensitive adhesive layer side was concave.

When bonding a polarizing plate to a liquid crystal cell, an adhesive layer is formed in the outer side of a transparent resin film, and a polarizing plate is bonded to a liquid crystal cell through the adhesive layer. In this case, the reversed polarizing plate has a concave shape on the side of the pressure-sensitive adhesive layer, but if there is a slight reverse curl, there is no problem. . For this reason, problems, such as deterioration of the optical characteristic resulting from foam | bubble, a fall of bonding strength, tend to arise.

On the contrary, what is called a positive curl state in which the adhesive layer side becomes convex can also be considered. Since the central portion of the pressure sensitive adhesive layer is convex, the polarizing plate of the regular curl can be adhered to the liquid crystal cell by pushing the central portion of the pressure sensitive adhesive layer, and the adhesive can be bonded while letting air out around. It becomes easy and is preferable. However, when the excessive curl is excessively large, this time the polarizing plate is about to be curled, so that the adhesion is peeled off from the edge of the polarizing plate adhered to the surface of the liquid crystal cell, so that lifting occurs and the polarizing plate is easily peeled off from the liquid crystal cell. Problems are likely to occur.

An object of the present invention is to provide a method for producing a polarizing plate in which excessive reverse curl is unlikely to occur and the optical characteristics and the bonding strength are good.

According to the manufacturing method of the polarizing film of this invention, the said subject is a polyvinyl alcohol-type resin film and the polyvinyl alcohol-type resin film adsorbed and orientated on one side of the polarizing film which has a dichroic dye. The acrylic resin film is bonded together, and the other surface of the said polarizing film is solved by the method of bonding a transparent resin film through an adhesive agent, and manufacturing a polarizing plate. The manufacturing method of this invention conveys (A) the raw material film which conveys the said polarizing film, the said acrylic resin film, and the said transparent resin film so that the said polarizing film may be sandwiched between the said acrylic resin film and the said transparent resin film. The said acrylic resin film is laminated | stacked on the single side | surface of the said polarizing film, and the said transparent resin film on the other surface of the said polarizing film via a curable adhesive agent, and contact | connects with the said acrylic resin film, and the said acryl-type The said acrylic resin film / the said polarizing film / the said transparent resin film by the 1st bonding roll which rotates in the conveyance direction of a resin film, and the 2nd bonding roll which contacts a said transparent resin film, and rotates in the conveyance direction of the said transparent resin film. The said adhesive agent hardens after the joining process which performs the said bonding by sandwiching the laminated body of (C), and the said bonding process (B). Kigo, the acrylic resin film and the transparent resin film includes a step of curing the adhesive and the polarizing film. In the said bonding process (B), the shrinkage stress in the said conveyance direction in the said acrylic resin film side of the said laminated body rather than the shrinkage stress in the said conveyance direction in the said transparent resin film side of the said laminated body The transparent resin film and the acrylic resin film are bonded to the polarizing film in a state where tension is applied to the transparent resin film and the acrylic resin film so as to become large.

In this case, the said bonding process (B) is the said transparent resin film (of the said transparent resin film) with respect to the circumferential speed of the 1st bonding roll which contacts the said acrylic resin film (the outer side of the said acrylic resin film). It is preferable to carry out so that the ratio of the circumferential speeds of the 2nd bonding rolls in contact with the outer side) may be 1.0105 or more and 1.0141 or less.

Or the said bonding process (B) per unit cross-sectional area of the said acrylic resin film before bonding to the said polarizing film with respect to the tension (tension before bonding) of the unit cross-sectional area of the said transparent resin film before bonding to the said polarizing film. It is preferable to perform so that the ratio of the tension (tension before joining) is 1 or more.

The method concerning this invention is suitable if it further includes the protective film bonding process of bonding a protective film to the surface on the opposite side to the surface bonded to the said polarizing film among the said acrylic resin films.

Moreover, it is preferable that the said transparent resin film is a film which is not extended | stretched, or is a film uniaxially or biaxially stretched.

And furthermore, the method which concerns on this invention apply | coats the said adhesive agent to the surface (bonding surface) joined to the said polarizing film of the said acrylic resin film in the middle of the said raw material film conveyance process (A), The said of the said transparent resin film It is suitable to further provide the adhesive agent application process which apply | coats the said adhesive agent to the surface (bonding surface) joined to a polarizing film.

It is preferable that the said adhesive agent contains an active energy ray hardening resin, and the said hardening process (C) is performed by hardening | curing the said active energy ray hardening resin by irradiation of an active energy ray.

According to the manufacturing method of the polarizing plate of this invention, a thin polarizing plate can be manufactured at low cost by using acrylic resin. In addition, both films are bonded to the polarizing film in a state where tension is applied to both films so that the shrinkage stress in the conveying direction at the acrylic resin film side is larger than the shrinkage stress at the conveying direction at the transparent resin film side. Doing. For this reason, a stronger shrinkage stress acts on the acrylic resin film side than on the transparent resin film side, and the force which the polarizing plate tries to bend to the acrylic resin film side acts. Thus, by making a difference in the shrinkage stress of both films, the excess reverse curl which corrects the convex shape by the acrylic resin film side becomes large due to the difference of the shrinkage stress of both films, etc., and the amount of reverse curl is made small, or the polarizing plate slightly You can do it with a normal. Thereby, it becomes possible to provide a polarizing plate excellent in optical characteristics and bonding strength by suppressing excessive reverse curl.

BRIEF DESCRIPTION OF THE DRAWINGS It is a cross-sectional schematic diagram which shows the process of bonding an acrylic resin film and a transparent resin film to a polarizing film.
2 is a perspective view illustrating a state in which a polarizer is normal and reversed.
3 is a perspective view schematically showing a method of measuring curl amount.
It is a cross-sectional schematic diagram of a polarizing plate.
5 is a graph showing the results of Examples and Comparative Examples.

(Description of a Suitable Example)

EMBODIMENT OF THE INVENTION Hereinafter, some embodiment of this invention is described with reference to drawings. In addition, this invention is not limited by the member, arrangement | positioning, etc. which are demonstrated below, These members etc. can be suitably modified according to the meaning of this invention.

Hereinafter, the manufacturing method of a polarizing plate is demonstrated in detail. 1: is a cross-sectional schematic diagram which shows the process of bonding an acryl-type resin film and a transparent resin film to a polarizing film. As shown in this figure, the acrylic resin film 25 is bonded to the single side | surface of the polarizing film 21 which consists of polyvinyl alcohol-type resin in which the oriented dichroic dye is adsorb | sucked through an adhesive agent. Moreover, the transparent resin film 23 is bonded to the other surface of the polarizing film 21 through an adhesive agent. The manufacturing method of the polarizing plate 20 of this embodiment is equipped with a raw material film conveyance process (A), a bonding process (B), and a hardening process (C). In addition, in this embodiment, the protective film bonding process (D) is performed.

In a raw material film conveyance process (A), while the polarizing film 21 is conveyed in a fixed direction, the acrylic resin film 25 is supplied to the one surface, and the transparent resin film 23 is supplied to the other surface. do. In the middle of a raw material film conveyance process (A), the adhesive agent is apply | coated to the surface (bonding surface) joined by the adhesive agent coating apparatus 12 to the polarizing film 21 of the acrylic resin film 25, and the other one adhesive agent coating apparatus is carried out. The adhesive agent is apply | coated to the surface (bonding surface) joined by the polarizing film 21 of the transparent resin film 23 by (13).

The bonding step (B) is the first bonding roll 15 in contact with the outer surface of the acrylic resin film 25 and the second bonding roll 16 in contact with the outer surface of the transparent resin film 23. And the laminated body of the acrylic resin film 25 / polarizing film 21 / transparent resin film 23 are performed. The 1st bonding roll 15 and the 2nd bonding roll 16 are rotating in the conveyance direction of the film which each contact, and the curve arrow in the figure has shown the rotation direction.

The curing step (C) supplies energy for curing the adhesive to the laminate obtained in the bonding step (B) from the curing device 18, and polarizes the light between the polarizing film 21 and the acrylic resin film 25. It is a process of hardening the adhesive agent between the film 21 and the transparent resin film 23. Hereinafter, each of these steps will be explained in order.

[Raw Film Transfer Process (A)]

In a raw material film conveyance process (A), the elongate polarizing film 21 is continuously sent out from the polarizing film 21 wound by roll shape. On one side of the polarizing film 21 sent at a predetermined speed, a long acrylic resin film 25 continuously fed from the acrylic resin film 25 wound in a roll shape is supplied. On the other hand, the other side of the polarizing film 21 is supplied with the elongate transparent resin film 23 continuously sent out from the transparent resin film 23 wound in the roll shape.

What is necessary is just to set the conveyance speed of each film to the value suitable for the manufacturing apparatus, and although it does not restrict | limit especially, Usually, it is the speed according to the conveyance speed of the polarizing film 21 manufactured and conveyed in a previous process. As long as the tact time is faster unless the kind and quality of the polarizing plate 20 are restricted, the higher the conveying speed is preferable from the viewpoint of productivity. Specifically, as a conveyance speed, it can set about 1-30 m / min, for example.

The direction in which each film is conveyed is not specifically limited, At the end of a conveyance process, each direction is fixed to the acrylic resin film 25 and the transparent resin film 23 in the fixed direction which the polarizing film 21 is sandwiched between. What is necessary is just to convey a film. In the intermediate step, for example, there may be a part in which the acrylic resin film 25 and the transparent resin film 23 are conveyed in the vertical direction as shown in the drawing with respect to the conveying direction of the polarizing film 21, There may be a part conveyed in parallel. In addition, when there exists a restriction | limiting in the arrangement | positioning of a manufacturing apparatus, after the acrylic resin film 25 and the transparent resin film 23 continue to send out in the reverse direction to the conveyance direction of the polarizing film 21 once, it polarizes with a suitable roll. It may be redirected and conveyed so that it may face one side of the film 21. Moreover, after continuing to export at the suitable angle containing a vertical direction from the side direction from which the polarizing film 21 is conveyed, it may be redirected and conveyed so that it may face one side of the polarizing film 21 with a suitable roll.

[Protective film bonding step (D)]

Although illustration is abbreviate | omitted, the acrylic resin film 25 can be provided to a raw material film conveyance process (A) in the state in which the protective film was laminated | stacked on the opposite side to the surface bonded to the polarizing film 21. FIG. The protect film has a role of protecting the surface of the acrylic resin film 25 and increasing the reliability of conveyance and bonding. Moreover, since a protective film has high rigidity and there is what is called "elasticity," a film is shape | molded by bonding a protective film to the acrylic resin film 25 or the polarizing plate 20 provided with this, and it curls. There is also the effect of suppressing. In this case, the acrylic resin film 25 is provided to a raw material film conveyance process (A) after passing through the protective film bonding process which bonds a protective film. In addition, this protective film bonding process (D) is not an essential process in this invention, but is an arbitrary process.

Bonding machines, such as a roll type lamination, can be used for joining the acrylic resin film 25 and a protective film. In this protective film bonding process (D), the tension before bonding of the acrylic resin film 25 and the tension before bonding of a protective film may be the same, or may differ.

Although the method of adjusting the tension before each bonding is not specifically limited, For example, the method of adjusting the torque applied to the bonding roll of the film with which the bonding apparatus was equipped, and the torque applied to the film roll or pinch roll which are continuously sent out, and bonding The method etc. which generate | occur | produce a tension by placing a micro difference in the circumferential speed of a roll and the circumferential speed of the film roll or pinch roll which are continuously sent out can be employ | adopted.

[Adhesive Coating Process]

Bonding between the polarizing film 21 and the acrylic resin film 25 and bonding between the polarizing film 21 and the transparent resin film 23 are performed via an adhesive agent. The adhesive agent is a bonding surface of the polarizing film 21 and transparent resin in at least one of the bonding surface of the polarizing film 21 and the bonding surface of the acrylic resin film 25 at any stage in a raw material film conveyance process (A). It can apply to at least one of the bonding surfaces of the film 23, respectively. In the figure, although the adhesive agent is apply | coated to the bonding surface of the acrylic resin film 25 using the adhesive agent coating apparatus 12, and the bonding surface of the transparent resin film 23 using the adhesive agent coating apparatus 13, respectively, The surface which apply | coats an adhesive agent is not limited to this. For example, an adhesive may be applied to the bonding surface of the polarizing film 21 instead of the acrylic resin film 25 or the transparent resin film 23, or the acrylic resin film 25, the transparent resin film 23, and polarized light. You may apply an adhesive agent to all the bonding surfaces of the film 21.

However, it is preferable to apply an adhesive agent to the surface bonded to the polarizing film 21 of each of the acrylic resin film 25 and the transparent resin film 23 from a viewpoint of operability. That is, in the raw material film conveying process (A), in contrast to the subsequent bonding process (B), the part conveyed so that the polarizing film 21 may be sandwiched by the acrylic resin film 25 and the transparent resin film 23 is interposed. Since this exists, it is preferable to apply | coat an adhesive agent in that part.

Therefore, Preferably, an adhesive agent coating process is performed in the middle of a raw material film conveyance process (A). An adhesive agent is apply | coated to the surface joined to the polarizing film 21 of each of the acrylic resin film 25 and the transparent resin film 23 in this adhesive agent application process.

The adhesive surface of the acrylic resin film 25 and the transparent resin film 23 may be subjected to surface activation treatment such as corona treatment, plasma treatment, ultraviolet irradiation treatment, or electron beam irradiation treatment before the adhesive is applied. In addition, each film may be subjected to washing and drying as necessary, and may be subjected to application of an anti-adhesive treatment agent or surface modifier and the like and subsequent drying treatment.

The structure and application method of the adhesive application devices 12 and 13 are not specifically limited, What is necessary is just to employ | adopt the apparatus and method which can apply | coat a required amount of adhesive uniformly. For example, various coating methods, such as a doctor blade, a wire bar, die coating, a comma coating, and gravure coating, can be employ | adopted.

[Joining Step (B)]

In a raw material film conveyance process (A), the acryl-type resin film 25 and the transparent resin film 23 supplied from both sides of the polarizing film 21 so that the polarizing film 21 may be interposed are continued bonding process (B). Is supplied. In this bonding process (B), by the 1st bonding roll 15 which contacts the outer side of the acrylic resin film 25, and the 2nd bonding roll 16 which contacts the outer side of the transparent resin film 23, The film is bonded.

Here, when normal bonding conditions, ie, the circumferential speed of the 1st bonding roll 15 and the circumferential speed of the 2nd bonding roll 16, are the same, the polarizing plate 20 obtained has the acrylic resin film 25 side The convex and transparent resin film 23 sides are concave, and excessive reverse curl is likely to occur. So, in this embodiment, in the bonding process (B), both shrinkage stress in the acrylic resin film 25 side becomes larger than shrinkage stress in the conveyance direction in the transparent resin film 23 side, Both films 23 and 25 are bonded to the polarizing film 21 in the state which tensioned the films 23 and 25. FIG.

Thus, although there exist various methods as a method of providing tension to both films 23 and 25, the following two embodiments are mentioned, for example.

(B-1) of the peripheral speed of the second bonding roll 16 in contact with the outside of the transparent resin film 23 with respect to the peripheral speed of the first bonding roll 15 in contact with the outside of the acrylic resin film 25. The ratio is made 1.0105 or more and 1.0414 or less.

(B-2) The ratio of the tension before bonding per unit cross-sectional area of the acrylic resin film 25 to the tension before bonding per unit cross-sectional area of the transparent resin film 23 is made 1 or more.

Hereinafter, embodiment of said (B-1) and (B-2) is demonstrated in order.

(B-1) First Embodiment

In this embodiment, in a joining process (B), it joins so that ratio of the circumferential speed of the 2nd bonding roll 16 with respect to the circumferential speed of the 1st bonding roll 15 may be 1.0105 or more and 1.0141 or less. This circumferential relationship means that the following formula (1) is satisfied by setting the circumferential speed of the first bonding roll 15 as R ₁ and the circumferential speed of the second bonding roll 16 as R ₂ .

1.0105≤R ₂ / R ₁ ≤1.0141 (1)

Due to the ratio of the main speeds, the acrylic resin film 25 is continuously sent out along the conveying direction with a large force, and the transparent resin film 23 is continuously sent out along the conveying direction with a smaller force. For this reason, the acrylic resin film 25 will be in the state to which tension was added compared with the transparent resin film 23. Thereby, the shrinkage stress is relatively given to the acrylic resin film 25, and the tensile stress is relatively given to the transparent resin film 23, respectively, and is conveyed to the next curing step (C), and the adhesive is cured. As a result, the polarizing plate 20 will be in a state near flatness by the difference of the shrinkage stress of the acrylic resin film 25 and the transparent resin film 23.

When the ratio of the circumferential speed of the second bonding roll 16 to the circumferential speed of the first bonding roll 15 decreases, the polarizing plate tends to be inverted as shown in Fig. 2 (a), and on the contrary, when the ratio of the circumferential speed increases, The polarizing plate tends to be the normal curl shown in Fig. 2B.

When the ratio of the circumferential speed of the second gluing roll 16 to the circumferential speed of the first bonding roll 15 is less than 1.0105, the curl amount of the reverse curl is too large, and bubbles are easily trapped at the time of bonding to the liquid crystal cell 40. There is a possibility of quality. As the ratio of the main speed increases, the curl amount of the reverse curl decreases and becomes flat, and when a certain value is exceeded, the transparent resin film 23 side becomes a convex static curl this time. If the amount of curl is small and a little normal curl, since an adhesive layer becomes convex, when a polarizing plate 20 is bonded to the liquid crystal cell 40, a bubble etc. become difficult to enter and it is preferable. However, if the ratio of the circumferential speed of the second gluing roll 16 to the circumferential speed of the first bonding roll 15 exceeds 1.0141, the curl amount of the normal curl becomes too large this time, and the polarizing plate (after bonding to the liquid crystal cell 40) There is a possibility that the problem that 20) easily comes off from the liquid crystal cell 40 tends to occur.

When the normal curl is positive (+) and the reverse curl is negative (-), the amount of curl is preferably in the range of about -80 to +80 mm, and the ratio of the circumferential speed within the range of this curl amount is also shown in the examples described later. It is 1.0105 or more and 1.0141 or less. Thus, the second by more than the peripheral velocity (R ₁₎ of the bonding roll a peripheral speed (R ₂₎ of 16, first bonding roll 15 is slightly larger, by setting the proton ratio to be in the above range, a polarizing plate obtained The reverse curl and the static curl of (20) do not become excessive, and the amount of curl is certainly controlled appropriately.

In addition, the curl amount of the polarizing plate 20 is measured as follows. First, the polarizing plate 20 is cut to an appropriate size along the flow direction MD of the roll-shaped polarizing plate 20. As size, it cuts to arbitrary sizes, such as 250 mm x 300 mm, or 400 mm x 700 mm. When indicating the curl amount, it is necessary to specify the measured size. As shown in FIG. 3, when curl is generated in the polarizing plate 20, the convex side is faced downward, and when curl is not generated, which side is faced downward. Then, it is placed on a reference plane (for example, on a horizontal table) and allowed to stand for 1 hour in an environment of a temperature of 22 ° C. and a relative humidity of 60%. In this figure, the surface when it is assumed that there is no curl in the polarizing plate 20 is shown as an imaginary surface (surface shown by the dotted line in drawing) shown by the square ABCD. When curling was not observed initially, if the lower part was convex after standing for 1 hour in an environment of a temperature of 22 ° C. and a relative humidity of 60%, the amount of curl was measured as shown below, but if the upper part was convex after standing for 1 hour The front and back of the polarizing plate 20 are inverted and the curl amount is measured by the method shown below. On the other hand, if the curl is not observed in the first placed state even after 1 hour of standing, the front and rear sides of the polarizing plate 20 are inverted. When curl is observed, the curl amount is measured by the method shown below in that state. When curl is observed, as shown in the figure, the amount of curl is measured with the convex side facing down.

3 (a) shows the inverted polarizing plate 20 in which the transparent resin film 23 side is concave and the acrylic resin film 25 side is convex. In the reversed polarizing plate 20, the acrylic resin film 25 side is provided downward on the reference plane. In the reversed polarizing plate 20, one corner A on the imaginary plane becomes the position of A1, and the other corners B, C, and D become the positions of B1, C1, and D1, respectively. That is, in this figure, although the four corners A1, B1, C1 and D1 of the polarizer 20 are all floating, one, two or three of the four corners of the polarizer 20 are lifted up. It may not be. Of course, without curl at all, the four corners A1, B1, C1, and D1 all match the square ABCD of the virtual plane. In this state, for each of the four corners A1, B1, C1, and D1 of the polarizing plate 20, the height H from the reference plane is measured, and the maximum amount is used as the curl amount.

On the other hand, FIG.3 (b) has shown the normalized polarizing plate 20 in which the transparent resin film 23 side was convex, and the acrylic resin film 25 side was concave. In the normalized polarizing plate 20, the transparent resin film 23 side is provided downward on the reference plane. In the same manner as the above inverse curl, the height H from the reference plane is measured for each of the four corners A1, B1, C1, and D1 of the polarizing plate 20, and the maximum amount is used as the amount of curl.

Materials constituting the surfaces of the joining rolls 15 and 16 include metals such as stainless steel, copper alloy, and chrome plated products;

Rubbers such as polyurethane, polyfluoroethylene, silicone;

Ceramics obtained by thermally spraying one kind or two or more kinds of chromium oxide, silicon oxide, zirconium oxide, and aluminum oxide;

Etc. can be mentioned. Especially, it is preferable that the 1st bonding roll 15 is made into a rubber roll, and the 2nd bonding roll 16 is made into a metal roll. That is, by applying a rubber roll having elasticity to the surface of the acrylic resin film 25 having a relatively thin and weak rigidity, and generally placing a metal roll on the transparent resin film 23 side having a relatively higher rigidity than the acrylic resin film 25. The stress generated by the difference between the main speeds of both can be effectively and uniformly applied to the film.

(B-2) Second Embodiment

In this embodiment, bonding is performed so that the ratio of the tension before bonding per unit cross-sectional area of the acrylic resin film 25 to the tension before bonding per unit cross-sectional area of the transparent resin film 23 may be 1 or more. That is, by bonding in a state where a greater tension is applied to the acrylic resin film 25 side than the transparent resin film 23, a larger shrinkage stress is generated on the acrylic resin film 25 side and excessive reverse curl is suppressed. Here, the tension before bonding can be given to the film before bonding by tensioning in the direction along the conveyance direction of a film. Specifically, the winding roll (not shown) which winds up the polarizing plate 20 in roll shape rather than the feeding roll (not shown) which draws out the roll-shaped acrylic resin film 25, for example. The method of making a difference in the rotational speed of both rolls so that a winding force may become large is mentioned.

Here, the pre-bonding tension per unit cross-sectional area means the pre-bonding tension applied to the film per unit cross-sectional area in the width direction of the film, and can be specifically expressed by the following formula (2).

Pre-bonding tension per unit cross-sectional area (N / mm2) = Pre-bonding tension (N) / cross-sectional area in the film width direction (mm2) (2)

For example, when the tension before bonding of the film is 1000 N and the cross-sectional area in the film width direction is 2000 mm 2, the tension before bonding per unit cross-sectional area is 0.50 (N / mm 2).

In this embodiment, the ratio of the tension before joining per unit cross-sectional area is adjusted so that following formula (3) may be satisfied.

Ratio of pre-bonding tension per unit cross-sectional area = pre-bonding tension per unit cross-sectional area of acrylic resin film 25 / pre-bonding tension per unit cross-sectional area of transparent resin film 23 ≥ 1 kPa (3)

It is preferable that the ratio of this tension before joining is one or more. When this ratio of tension before joining is less than 1, there exists a possibility that the excessive reverse curl which becomes a large convex shape on the acrylic resin film 25 side will become easy to produce. Although the upper limit of the ratio of the tension before joining is not specifically limited, It is preferable that it is two or less. This is because when the ratio of tension before joining exceeds 2, it becomes easy to become excessive static curl this time.

In addition, although the main speed ratio of 1st Embodiment (B-1) and the tension ratio before joining of 2nd Embodiment (B-2) have an effect which suppresses reverse curl by only one, the main speed ratio and tension before joining are shown. By satisfying both of the ratios, a higher effect can be obtained. That is, with respect to the pre-bonding tension per unit cross-sectional area of the transparent resin film 23 while the main speed ratio of the second bonding roll 16 to the main speed ratio of the first bonding roll 15 is 1.0105 or more and 1.0414 or less. The ratio of the tension before bonding per unit cross-sectional area of the acrylic resin film 25 is made 1 or more. Thereby, larger shrinkage stress is generated in the acrylic resin film 25 than in the transparent resin film 23, and it becomes possible to suppress excessive reverse curl more reliably.

Curing Step (C)

The laminated body joined in the order of the acrylic resin film 25 / adhesive agent (not shown) / polarizing film 21 / adhesive agent (not shown) / transparent resin film 23 conveyed from the bonding process (B) is In the curing step (C), the adhesive is cured, and the acrylic resin film 25 and the transparent resin film 23 are bonded to the polarizing film 21, respectively, to form a polarizing plate 20. In the figure, the laminated body bonded by the bonding rolls 15 and 16 is sent to the hardening apparatus 18, and hardening process is performed there. Hardening process can be performed by irradiation of an active energy ray, heating, drying, etc. according to the kind of adhesive agent.

As an adhesive agent, it is preferable to use the active energy ray curable adhesive hardened | cured by irradiation of an active energy ray. In this case, a hardening process (C) is performed by irradiation of an active energy ray. The active energy ray used for curing the adhesive may be, for example, X-rays having a wavelength of 1 pm to 10 nm, ultraviolet rays having a wavelength of 10 to 400 nm, visible rays having a wavelength of 400 to 800 nm, or the like. Especially, an ultraviolet-ray is used preferably from a viewpoint of the ease of handling, the ease of preparation of a curable adhesive composition, its stability, and its hardening performance. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, etc., having a light emission distribution at a wavelength of 400 nm or less can be used as the light source. have.

The irradiation intensity of the ultraviolet ray is determined depending on the type of the adhesive and the irradiation time, and is not particularly limited. For example, it is preferable to set the irradiation intensity of the wavelength region effective for the activation of the initiator to be 0.1 to 300 mW / cm 2, Furthermore, it is more preferable to set so that it may become 1-200mW / cm <2>. When the light irradiation intensity | strength to curable adhesive composition is less than 0.1 mW / cm <2>, hardening reaction time will become long and it will become hard to harden | cure unless you lengthen irradiation time, and it becomes disadvantageous in terms of productivity. On the other hand, when light irradiation intensity | strength exceeds 300 mW / cm <2>, when yellowing of a curable adhesive composition and deterioration of the polarizing film 21 are caused by the heat radiated | emitted from a lamp | ramp, and the heat | fever at the time of superposition | polymerization of a curable adhesive composition. There is.

Although the irradiation time of an ultraviolet-ray also depends on the kind of adhesive and irradiation intensity, it does not restrict | limit, For example, it is preferable to set so that accumulated light quantity represented by the product of irradiation intensity and irradiation time may be set to 10-5,000 mJ / cm <2>. Furthermore, it is more preferable to set so that it may become 50-1,000mJ / cm <2>. When the amount of accumulated light in the curable adhesive composition is less than 10 mJ / cm 2, generation of the active species derived from the initiator will not be sufficient, and curing of the resulting adhesive layer will be insufficient. On the other hand, when accumulated light amount exceeds 5,000 mJ / cm <2>, since irradiation time becomes very long, it becomes easy to become disadvantageous in terms of productivity.

When performing a hardening process (C) by irradiation of an active energy ray, although the thickness of the hardened adhesive bond layer is 1 micrometer or more and 50 micrometers or less normally, it is 20 micrometers or less from a viewpoint of thinning the polarizing plate 20 by maintaining moderate adhesive force. Is preferable, and furthermore, 10 micrometers or less are more preferable.

As mentioned above, one Embodiment of the manufacturing method of the polarizing plate 20 was demonstrated. Moreover, in embodiment mentioned above, while performing the raw material film conveyance process (A), the protective film bonding process (D) which bonds a protective film to the acrylic resin film 25 is performed, and thereafter, the bonding process (B) And the curing step (C). However, the timing of performing the protective film bonding step (D) is not limited to the above-described raw film transfer step (A). For example, a raw material film conveyance process (A), a bonding process (B), and a hardening process (C) are performed, and the laminated body of the acrylic resin film 25 / polarizing film 21 / transparent resin film 23 is manufactured. After that, the protective film bonding step (D) may be performed to bond the protective film to the surface of the acrylic resin film 25.

(Polarizing plate 20)

Next, the polarizing plate 20 will be described. As shown in FIG. 4, the polarizing plate 20 is equipped with the laminated constitution which the acrylic resin film 25, the polarizing film 21, and the transparent resin film 23 laminated | stacked in this order. Hereinafter, each layer which comprises the polarizing plate 20 is demonstrated.

(1) polarizing film (21)

The polarizing film 21 is a member having a function of converting natural light into linearly polarized light. As the polarizing film 21, one which adsorbs and orients a dichroic dye to a uniaxially stretched polyvinyl alcohol-based resin film can be used. As polyvinyl alcohol-type resin, what saponified polyvinyl acetate type resin can be used, As polyvinyl acetate type resin, In addition to polyvinyl acetate which is a homopolymer of vinyl acetate, And copolymers thereof are exemplified. As another monomer copolymerizable with vinyl acetate, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamide which has an ammonium group, etc. are mentioned, for example.

The sensitivity of polyvinyl alcohol-type resin is about 85-100 mol% normally, Preferably it is 98 mol% or more. The polyvinyl alcohol-based resin may be modified. For example, polyvinyl formal, polyvinyl acetal, or the like modified with aldehydes can also be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

What formed such a polyvinyl alcohol-type resin into a film is used as a raw film of the polarizing film 21. The method of forming a polyvinyl alcohol-type resin into a film is not specifically limited, It can form into a film by a well-known method. Although the thickness of a polyvinyl alcohol-type raw film is not specifically limited, For example, it is about 5-150 micrometers.

The polarizing film 21 is usually a step of uniaxially stretching such a polyvinyl alcohol-based resin film, a step of adsorbing the dichroic dye by dyeing the polyvinyl alcohol-based resin film with a dichroic dye, and a dichroic dye adsorbed. It manufactures through the process of processing a polyvinyl alcohol-type resin film with aqueous solution of boric acid, and the process of washing with water after the process by aqueous solution of boric acid.

Uniaxial stretching of a polyvinyl alcohol-type resin film can be performed before dyeing with a dichroic dye, simultaneously with dyeing, or after dyeing. When performing uniaxial stretching after dyeing, this uniaxial stretching may be performed before boric acid treatment, and may be performed during boric acid treatment. Moreover, uniaxial stretching can also be performed in several steps. As uniaxial stretching, the method of extending | stretching to 1 axis between rolls from which a circumferential speed differs, the method of extending | stretching to 1 axis using a thermal roll, etc. can be employ | adopted. In addition, uniaxial stretching may be dry extending | stretching extending | stretching in air | atmosphere, and wet extending | stretching may be performed in the state which swelled the polyvinyl alcohol-type resin film using solvents, such as water. A draw ratio is about 3 to 8 times normally.

Dyeing by the dichroic dye of a polyvinyl alcohol-type resin film can be performed by the method of immersing a polyvinyl alcohol-type resin film in the aqueous solution containing a dichroic dye, for example. As a dichroic dye, an iodine or a dichroic dye is used specifically ,. In addition, it is preferable that the polyvinyl alcohol-based resin film is subjected to a treatment of swelling by immersion in water before dyeing treatment.

When using iodine as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type resin film in the aqueous solution containing iodine and potassium iodide is employ | adopted normally.

Content of iodine in this aqueous solution is about 0.01-1 weight part normally per 100 weight part of water, and content of potassium iodide is about 0.5-20 weight part normally per 100 weight part of water. The temperature of the aqueous solution used for dyeing is about 20-40 degreeC normally. In addition, the immersion time (dyeing time) in this aqueous solution is about 20-1,800 second normally.

On the other hand, when using a dichroic dye as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type resin film in the aqueous solution containing water-soluble dichroic dye is employ | adopted normally. Content of the dichroic dye in this aqueous solution is about 1 * 10 <^-4> -10 weight part normally per 100 weight part of water, Preferably it is about 1 * 10 <^-3> -1 weight part. This aqueous solution may contain inorganic salts, such as sodium sulfate, as a dyeing adjuvant. The temperature of the dichroic dye aqueous solution used for dyeing is about 20-80 degreeC normally. In addition, the immersion time (dyeing time) in this aqueous solution is about 10 to 1,800 second normally.

The boric acid treatment after dyeing with a dichroic dye can be performed by immersing the dyed polyvinyl alcohol-type resin film in boric acid containing aqueous solution. Content of boric acid in boric-acid containing aqueous solution is about 2-15 weight part normally per 100 weight part of water, Preferably it is about 5-12 weight part. When using iodine as a dichroic dye, it is preferable that this boric acid containing aqueous solution contains potassium iodide. Content of potassium iodide in boric-acid containing aqueous solution is about 0.1-15 weight part normally per 100 weight part of water, Preferably it is about 5-12 weight part. Immersion time in boric-acid containing aqueous solution is about 60-1,200 second normally, Preferably it is about 150-600 second, More preferably, it is about 200-400 second. The temperature of boric-acid containing aqueous solution is 50 degreeC or more normally, Preferably it is 50-85 degreeC, More preferably, it is 60-80 degreeC.

The polyvinyl alcohol-based resin film after boric acid treatment is usually washed with water. A water washing process can be performed by immersing the polyvinyl alcohol-type resin film processed by boric acid in water, for example. The temperature of the water in a water washing process is about 5-40 degreeC normally, and immersion time is about 1-120 second normally.

After water washing, a drying process is performed and the polarizing film 21 is obtained. A drying process can be performed using a hot air dryer or a far infrared heater. The temperature of a drying process is about 30-100 degreeC normally, Preferably it is 50-80 degreeC. The time of a drying process is about 60 to 600 second normally, Preferably it is 120 to 600 second.

In this way, the polyvinyl alcohol-based resin film is subjected to uniaxial stretching, dyeing with a dichroic dye, and boric acid treatment to obtain a polarizing film 21. The thickness of the polarizing film 21 can be about 2-40 micrometers, for example.

It is preferable to provide the obtained polarizing film 21 to a raw material film conveyance process (A) as it is. Thereby, starting from the raw film of polyvinyl alcohol-type resin, it can produce continuously until the polarizing plate 20 is manufactured.

(2) acrylic resin film (25)

The acrylic resin film 25 is a member having functions such as anti-wear and reinforcement of the surface of the polarizing film 21 and is composed of acrylic resin. Here, acrylic resin means (meth) acrylic-type resin, and is a concept containing both acrylic resin and methacryl-type resin. Hereinafter, acrylic resin is demonstrated.

(2-1) acrylic resin

Acrylic resin is (meth) acrylic-type resin as mentioned above and means the polymer of acrylic acid ester and methacrylic acid ester. As a polymer of methacrylic acid ester, what consists of a polymer mainly having alkyl methacrylate, for example is preferable. As for the monomer composition of alkyl methacrylate, based on 100 weight% of total monomers, alkyl methacrylate becomes like this. Preferably it is 70 weight% or more, More preferably, it is 80 weight% or more, More preferably, Is 90 weight% or more, and the alkyl methacrylate is 99 weight% or less. Moreover, as acrylic resin, the homopolymer of alkyl methacrylate may be sufficient, and the copolymer of 50 weight% or less of monomers other than alkyl methacrylate 50weight% or more and alkyl methacrylate may be sufficient. As alkyl methacrylate, the C1-C4 thing of the alkyl group is used normally, Especially methyl methacrylate is used preferably.

In addition, the monomer other than the alkyl methacrylate may be a monofunctional monomer having one polymerizable carbon-carbon double bond in the molecule, or may be a polyfunctional monomer having two or more polymerizable carbon-carbon double bonds in the molecule. In particular, monofunctional monomers are preferably used, and examples thereof include alkyl acrylates such as methyl acrylate and ethyl acrylate, styrene monomers such as styrene and alkyl styrene, and unsaturated nitriles such as acrylonitrile and methacrylonitrile. . When alkyl acrylate is used as a copolymerization component, the carbon number is 1-8 normally.

Moreover, as acrylic resin, what does not have a glutarimide derivative, a glutaric anhydride derivative, a lactone ring structure, etc. is preferable. These acrylic resins may not obtain sufficient mechanical strength and heat-and-moisture resistance as the acrylic resin film 25.

(2-2) rubber elastomer particles

In order to improve flexibility and improve handling property, the acrylic resin film may contain rubber elastomer particles. The rubber elastic body particles are particles containing a rubber elastic body and may be particles composed only of a rubber elastic body, or may be particles of a multilayer structure having a layer of rubber elastic body. As a rubber elastic body, an olefinic elastomer, a diene elastomer, a styrene diene elastomer, and an acrylic elastomer are mentioned, for example. Especially, an acrylic elastomer is used preferably from the surface hardness, light resistance, and transparency point of the acrylic resin film 25.

It is preferable that an acrylic elastomer is a polymer mainly having alkyl acrylate, and may be a homopolymer of alkyl acrylate, and may be a copolymer of 50 weight% or more of alkyl acrylate and 50 weight% or less of monomers other than alkyl acrylate. As alkyl acrylate, the C4-C8 thing of the alkyl group is used normally.

Examples of monomers other than alkyl acrylate include alkyl methacrylates such as methyl methacrylate and ethyl methacrylate, styrene monomers such as styrene and alkyl styrene, and unsaturated nitriles such as acrylonitrile and methacrylonitrile. Monofunctional monomers, alkenyl esters of unsaturated carboxylic acids such as allyl (meth) acrylic acid and (meth) acrylic acid metaallyl, dialkyl esters of dibasic acids such as diallyl maleic acid, and alkylene glycol di (meth) acrylates Polyfunctional monomers, such as unsaturated carboxylic acid diester of such glycols, are mentioned.

The rubber elastomer particles containing an acrylic elastomer are preferably particles of a multilayer structure having a layer of an acrylic elastomer, and are two-layer structures having a layer of a polymer mainly composed of alkyl methacrylate on the outside of the acrylic elastomer. It may be used, or may be a three-layer structure having a layer of a polymer mainly composed of alkyl methacrylate inside the acrylic elastomer. In addition, the monomer composition of the polymer mainly having the alkyl methacrylate which comprises the layer formed in the outer side or inside of an acrylic elastomer is a monomer of the polymer mainly having the alkyl methacrylate mentioned as an example of acrylic resin. It is the same as the example of a composition. Such acrylic rubber elastomer particles having a multilayer structure can be produced by, for example, the method described in JP-A-55-27576.

The number average particle diameter of the rubber elastic body contained in the rubber elastic body particles may be 10 to 300 nm. Thereby, when the acrylic resin film 25 is laminated | stacked on the polarizing film 21 using an adhesive agent, the acrylic resin film 25 can be made to be difficult to peel off from an adhesive bond layer. The number average particle diameter of this rubber elastic body becomes like this. Preferably it is 50 nm or more and 250 nm or less.

When the outermost layer is a polymer mainly composed of methyl methacrylate, and the rubber elastomer particles in which the acrylic elastomer is wrapped therein are mixed with the acrylic resin which is the mother, the outermost layer of the rubber elastomer particles is mixed with the acrylic resin which is the mother. )do. Therefore, when the cross section of an acryl-type resin film is dyed with the acryl-type elastomer with ruthenium oxide, and it is observed with an electron microscope, the rubber elastic body particle is observed as particle | grains of the state except the outermost layer. Specifically, when the inner layer is an acrylic elastomer and the outer layer is a two-layered rubber elastomer particle whose polymer is mainly methyl methacrylate, the acrylic elastomer part of the inner layer is dyed and observed as particles of a single layer structure. do. In addition, when the innermost layer is a polymer mainly composed of methyl methacrylate, the middle layer is an acrylic elastomer, and the outermost layer is a rubber elastomer particle having a three-layer structure, which is a polymer mainly composed of methyl methacrylate, The particle center portion of is not dyed, and only the acrylic elastomeric portion of the intermediate layer is observed as the dyed two-layered particles.

In addition, in this specification, the number average particle diameter of rubber elastic body particle is the number of the diameter of the part which is dyed and observed in a substantially circular shape when the rubber elastic body particle is mixed with a mother resin, and the cross section is dyed with ruthenium oxide in this way. Average value.

As for the acrylic resin composition which forms the acrylic resin film 25, 25-45 weight% of rubber elastic body particles of 10-300 nm of number average particle diameters are mix | blended with transparent acrylic resin.

The acrylic resin composition may be prepared by, for example, obtaining rubber elastomer particles and then polymerizing a monomer which is a raw material of the acrylic resin in the presence thereof to produce an acrylic resin as a parent, and after obtaining the rubber elastomer particles and the acrylic resin. You may manufacture by mixing both by melt kneading | mixing and the like.

If necessary, the acrylic resin composition may contain colorants such as pigments and dyes, fluorescent brighteners, dispersants, thermal stabilizers, light stabilizers, infrared absorbers, ultraviolet absorbers, antistatic agents, antioxidants, lubricants, and solvents. good.

The ultraviolet absorber is added to improve durability by absorbing ultraviolet rays of 400 nm or less. As a ultraviolet absorber, well-known things, such as a benzophenone series ultraviolet absorber, a benzotriazole type ultraviolet absorber, and an acrylonitrile type ultraviolet absorber, can be used.

Among them, 2,2'-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol) and 2- (2'-hydride Oxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, 2, 2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, etc. are used suitably. Among these, 2,2'-methylenebis (4- (1,1,3,3- tetramethylbutyl) -6- (2H-benzotriazol 2-yl) phenol) is particularly preferable.

The concentration of the ultraviolet absorber can be selected in a range in which the transmittance of the wavelength of 370 nm or less of the acrylic resin film 25 is preferably 10% or less, more preferably 5% or less, even more preferably 2% or less. have. As a method of containing a ultraviolet absorber, the method of mix | blending a ultraviolet absorber in acrylic resin previously;

The method of supplying directly at the time of melt extrusion molding, etc. are mentioned, Any method may be employ | adopted.

Examples of the infrared absorber include nitroso compounds, metal complex salts thereof, cyanine compounds, squarylium compounds, thiol nickel complex salt compounds, phthalocyanine compounds, naphthalocyanine compounds, triallyl methane compounds, immonium compounds, and dimonium compounds. Compounds, naphthoquinone compounds, anthraquinone compounds, amino compounds, aluminum salt compounds, carbon black, indium tin oxide, antimony tin oxide, oxides, carbides, borides, and the like of metals belonging to groups 4A, 5A, or 6A of the periodic table. Infrared absorbers etc. are mentioned. It is preferable to select these infrared absorbers so that the whole infrared ray (light of the wavelength of about 800 nm-1100 nm) can be absorbed, and you may use two or more types together. The quantity of an infrared absorber can be suitably adjusted so that the light transmittance of the wavelength of 800 nm or more of the acrylic resin film 25 may be 10% or less, for example.

The glass transition temperature (Tg) of an acrylic resin composition has preferable inside of the range of 80-120 degreeC.

Moreover, it is preferable that acrylic resin composition is high in surface hardness at the time of shape | molding to a film, specifically, it is B or more in pencil hardness (load is 500 g, based on JISKK5600-5-4).

Moreover, as for an acrylic resin composition, it is preferable that bending elastic modulus (JIS # K7171) is 1500 MPa or less from a viewpoint of the flexibility of the acrylic resin film 25. This bending elastic modulus becomes like this. More preferably, it is 1300 Mpa or less, More preferably, it is 1200 Mpa or less. This bending elastic modulus is fluctuate | varied by the kind, quantity, etc. of acrylic resin and rubber elastic body particle | grains in an acrylic resin composition, For example, a bending elastic modulus generally becomes small, so that there is much content of rubber elastic body particle | grains. In addition, generally, the bending elastic modulus becomes smaller when using a copolymer of alkyl methacrylate, alkyl acrylate, etc. rather than using the homopolymer of alkyl methacrylate as acrylic resin.

As the rubber elastomer particles, the use of the acrylic elastomer particles of the two-layer structure is generally smaller than the use of the acrylic elastomer particles of the three-layer structure, and the bending elastic modulus is generally smaller, and the acrylic elastomer particles of the single layer structure are used. In general, the bending elastic modulus becomes smaller. Also, the smaller the average particle diameter of the rubber elastic body or the larger the amount of the rubber elastic body, the smaller the elastic modulus of the elastic rubber is. Then, it is preferable to adjust the kind and quantity of acrylic resin or rubber elastic body particle in the said predetermined range, and to make bending elastic modulus into 1500 Mpa or less.

In the case where the acrylic resin film 25 has a multilayer configuration, the layer that may be present in addition to the layer of the acrylic resin composition is not particularly limited in its composition, and for example, an acrylic resin or a composition thereof containing no rubber elastomer particles. A layer may be sufficient and the layer which consists of acrylic resin composition whose content of rubber elastic body particle | grains and the average particle diameter of the rubber elastic body in rubber elastic body particle | grains is outside of the said prescription | regulation may be sufficient.

Typically, it is a two-layer or three-layer structure, For example, the two-layered structure which consists of an acrylic resin which does not contain the layer / rubber elastic particle of an acrylic resin composition, or the layer of this composition may be sufficient, and the layer / rubber of an acrylic resin composition The three-layer structure which consists of a layer of the acrylic resin which does not contain an elastic body particle, or the layer / acrylic resin composition of this composition may be sufficient. What is necessary is just to make the surface of the layer of an acrylic resin composition the bonding surface with the polarizing film 21 for the acrylic resin film 25 of a multilayered constitution.

In addition, when making the acrylic resin film 25 into a multilayer structure, you may make content of rubber elastic body particle | grains and content of each layer of the said compounding agent mutually different. For example, the layer containing a ultraviolet absorber and / or an infrared absorber, and the layer which interposes this layer and does not contain an ultraviolet absorber and / or an infrared absorber may be laminated | stacked. Moreover, you may make content of the ultraviolet absorber of the layer of an acrylic resin composition higher than content of the ultraviolet absorber of the acrylic resin which does not contain rubber elastic particle, or the layer of this composition, Specifically, the former is preferably 0.5? 10 weight%, More preferably, you may be 1 to 5 weight%, The latter may preferably be 0 to 1 weight%, More preferably, you may be 0 to 0.5 weight%, and accordingly, the color tone of the polarizing plate 20 is made Ultraviolet rays can be blocked efficiently without deteriorating, and the fall of the polarization degree at the time of long-term use can be prevented.

The acrylic resin film 25 may be non-oriented, non-oriented, or may be extended. When the stretching treatment is not performed, the film thickness becomes thick, so that the layer film thickness of the polarizing plate 20 tends to be thick. On the other hand, since the film thickness is thick, the handleability of the acrylic resin film 25 becomes good. Such an acrylic resin film 25 can be obtained from the unstretched film (disk film) obtained by forming an acrylic resin composition into a film. On the contrary, in the case of stretching, the phase difference tends to be expressed, while the stretching makes the film thickness of the acrylic resin film 25 thin and the rigidity also improved. A stretched film can be manufactured by extending | stretching an unstretched film by arbitrary methods.

Acrylic resin can be formed into a film by arbitrary methods, and can be set as an unstretched film. It is preferable that this unstretched film is transparent and substantially does not have in-plane retardation. As the film forming method, for example, an extrusion molding method in which a molten resin is extruded into a film to form a film, and a solvent casting method for removing a solvent and forming a film after casting a resin dissolved in an organic solvent on a flat plate is adopted. can do.

As a specific example of the extrusion molding method, the method of forming a film in the state which sandwiched the acrylic resin composition between two metal rolls is mentioned, for example. It is preferable that the metal roll in this case is a mirror surface roll. Thereby, the unstretched film excellent in surface smoothness can be obtained. In addition, when obtaining what is a multilayer structure as the acrylic resin film 25, what is necessary is just to film an acrylic resin composition after multilayer extrusion with another acrylic resin composition. It is preferable that the thickness of the unstretched film obtained in this way is 5-200 micrometers, More preferably, it is 10 micrometers-85 micrometers.

The unstretched film which consists of acrylic resin can be extended | stretched by well-known methods, such as uniaxial stretching and biaxial stretching. As a stretching method, the tenter method using a tenter stretching machine is mentioned. The biaxial stretching may be simultaneous biaxial stretching which is simultaneously stretched in two stretching directions, or may be sequentially biaxial stretching which is stretched in another direction after stretching in a predetermined direction.

Next, the haze value of the acrylic resin film 25 is demonstrated. A haze value is a ratio of the diffuse light transmittance with respect to the total light transmittance at the time of irradiating a visible ray to a film, and it is recognized that a film is excellent in transparency, so that a haze value is small. In addition, an internal haze value shows the value which subtracted the haze value (external haze value) resulting from the surface shape of a film from the haze value of a film.

As described above, the haze value of the acrylic resin film 25 is 1.0% or less, more preferably 0.5% or less, and preferably, external haze value is 5% or less. When internal haze value is 1.0% and external haze value exceeds 5%, the light which permeate | transmits a film may scatter and display characteristics may fall when bonding to a liquid crystal display device.

Moreover, by surface-treating the acrylic resin film 25, it is possible to give the function which the acrylic resin film 25 single body did not have. For example, the acrylic resin film 25 can be subjected to a hard coating process from the viewpoint of preventing scratches on the surface in the assembling process of the liquid crystal module. Moreover, surface treatment, such as antistatic treatment, can also be performed. However, when forming the polarizing plate 20 using the acrylic resin film 25 as a protective film of a polarizing film, an antistatic function can be provided by performing surface treatment with said acrylic resin film 25. In addition, it can also be provided to the other part of the polarizing plate 20 in which this base film was incorporated, such as an adhesive layer. As surface treatment to the acrylic resin film 25, other antireflection treatment, antifouling treatment, etc. are mentioned. In addition, antiglare treatment may be performed in view of improvement of visibility, prevention of external light shining, reduction of moire due to interference between the prism sheet and the color filter, and the like.

(3) transparent resin film (23)

It is preferable that the transparent resin film 23 is comprised with resin excellent in transparency. As such resin, for example, an olefin resin containing cellulose resin, polycarbonate resin, polyvinyl alcohol resin, polystyrene resin, (meth) acrylate resin, cyclic olefin resin or polypropylene resin , Polyallylate resin, polyimide resin, polyamide resin and the like. It is preferable that the transparent resin film 23 is the unstretched film which is not extended | stretched, or the stretched film uniaxially or biaxially stretched.

When this transparent resin film 23 is a stretched film, suitable phase difference is provided by extending | stretching. The film provided with the phase difference may be a wavelength plate such as a quarter wave plate or a half wave plate, or may be a viewing angle compensation film. The film thickness of retardation film is about 10-200 micrometers normally, Preferably it is 20-120 micrometers.

When using a viewing angle compensation film as a retardation film, it is necessary to consider the mode employ | adopted for the liquid crystal cell 40. FIG. For example, in the case of the liquid crystal cell 40 in the vertical alignment (VA) mode, as the viewing angle compensation film, a polymer film having positive intrinsic birefringence is uniaxially stretched, and the index ellipsoid is n _×. > n _y ≒ n positive a plate, carried out this transverse stretching or sequential biaxial stretching with a relationship of _z, n _x> n _y> of the biaxial having the relation of n _z film, or n _x ≒ n _y> n _z A negative C plate having a relationship of can be used. Here, n _x is an index of refraction in the in-plane slow axis (x-axis) direction of the film, and n _y is an in-plane fast axis (y-axis: an axis perpendicular to the slow axis and in-plane). The refractive index, and n _z, is the refractive index in the thickness (z-axis) direction.

Especially as the transparent resin film 23, the biaxially stretched biaxial film is used preferably. When using a biaxial viewing angle compensation film, the N _z coefficient used as the biaxiality reference | standard is defined by following formula (4), and also the in-plane phase difference value (R _o when the film thickness is d). ) And the phase difference value R _{th in the} thickness direction are defined by the following equations (5) and (6), respectively.

N _z = (n _x -n _z ) / (n _x -n _y ) (4)

R _o = (n _x -n _y ) × d (5)

R _th = [(n _x + n _y ) / 2-n _z ] × d (6)

Further, from the above formulas (4) to (6), the relationship between the N _z coefficient, the in-plane retardation value _Ro and the retardation value R _{th in the} thickness direction can be expressed by the following equation (7). have.

N _z = R _th / R _o +0.5 (7)

When using a viewing angle compensation film as the transparent resin film 23, it is preferable that the in-plane phase difference value _Ro is in the range of 30-300 nm, especially the range of 50-260 nm. Moreover, it is preferable that _Nz coefficient exists in the range of 1.1-7, especially the range of 1.4-5. From these ranges, what is necessary is just to select the value of an optical characteristic suitably according to the viewing angle characteristic calculated | required by the liquid crystal display device applied.

In the case where the transparent resin film 23 is a retardation film, when bonding the polarizing film 21 and the retardation film, the angle formed by the absorption axis of the polarizing film 21 and the slow axis of the retardation film is appropriately selected according to the application. Do it. For example, when the retardation film is a viewing angle compensation film, the angle formed between the absorption axis of the polarizing film 21 and the slow axis of the viewing angle compensation film is substantially 0 ° or 90 °.

On the other hand, when the transparent resin film 23 is an unstretched film, the phase difference is hardly expressed and functions as a protective film of the polarizing film 21. The transparent resin film 23 as an unstretched film can be used suitably for the liquid crystal cell 40 of IPS (In 'Plane Switching) mode among the modes employ | adopted for the liquid crystal cell 40, for example.

(4) adhesive (not shown)

An adhesive agent is used for the bonding between the polarizing film 21 and the acrylic resin film 25 and the bonding between the polarizing film 21 and the transparent resin film 23. The adhesive is cured by irradiation of active energy rays, heating, drying, or the like, and the polarizing film 21, the acrylic resin film 25, the polarizing film 21, and the transparent resin film 23 are bonded to strength sufficient for practical use. What you can do is good. Specifically, the following adhesive compositions are mentioned, for example.

Cationically polymerizable photocurable adhesive composition formed by mix | blending a photocationic polymerization initiator with cationically polymerizable compounds, such as a glycidyl ether type epoxy compound, an alicyclic epoxy compound, and an oxetane compound;

Radically polymerizable photocurable adhesive composition formed by mixing an optical radical polymerization initiator with a radically polymerizable compound such as an acrylic compound;

A thermosetting adhesive composition formed by mixing a thermal polymerization initiator, that is, a thermal cationic generator or a thermal radical generator, with a cationically polymerizable or radically polymerizable compound shown above;

The aqueous adhesive composition which consists of aqueous solution or aqueous dispersion which mix | blended the water-soluble or hydrophilic crosslinkable epoxy compound or urethane compound with the water-soluble resin which has a reactive group like polyvinyl alcohol-type resin as needed.

An epoxy compound can obtain a commercial item easily. For example of a commercial item, "Epiclon (EPICOAT)" sold by Japan Epoxy Resin Co., Ltd., "Epiclon (EPICLON)" sold by DIC Co., Ltd., Totokasei Co., Ltd., respectively, under a brand name `` EPOTOTO '' sold, `` ADEKA RESIN '' sold from ADEKA, `` DENACOR '' sold from Nagase Chem-Tex Corporation, Dow Chemical "DOW EPOXY" sold by the company, "TEPIC" sold by Nissan Kagaku Kogyo Co., Ltd., etc. are mentioned.

Moreover, the alicyclic epoxy compound which the epoxy group couple | bonded with the saturated carbocyclic ring can also obtain a commercial item easily. For example, commercially available products include `` CELLOXIDE '' and `` CYCLOMER '' sold by Daisel Kagaku Kogyo Co., Ltd., and `` CYRACURE '' sold by Dow Chemical Co., Ltd. ) ”.

Curable adhesive composition containing an epoxy compound may contain active energy ray curable compounds other than an epoxy compound further. As active energy ray curable compounds other than an epoxy compound, an oxetane compound, an acryl compound, etc. are mentioned, for example. Especially, it is preferable to use an oxetane compound together in the point which can improve hardening rate in cation polymerization.

An oxetane compound can also obtain a commercial item easily. Examples of commercially available products include "ARONOXETANE" sold by Toagosei Co., Ltd. and "ETERNACOLL" sold by Ubeko Co., Ltd. as trade names.

Since the curable compound containing an epoxy compound and an oxetane compound makes the curable adhesive composition which mixes these the non-solvent, it is preferable to use what is not diluted with the organic solvent. In addition, it is preferable to use the powder or liquid of the compound alone or the organic solvent removed and dried also in the small amount component containing the photocationic polymerization initiator and the sensitizer which comprise the adhesive composition mentioned later rather than melt | dissolving in the organic solvent.

The photocationic polymerization initiator generates a cationic species by being irradiated with an active energy ray, for example, ultraviolet rays, and may be used to provide an adhesive strength and a curing rate required for the adhesive composition in which it is blended. For example, aromatic diazonium salts;

Onium salts such as aromatic iodonium salts and aromatic sulfonium salts;

Iron-Allene complex etc. are mentioned. These photocationic polymerization initiators may be used independently, respectively and may use different multiple types together.

A photocationic polymerization initiator can also obtain a commercial item easily. For example, commercially available products are sold from Nippon Kayaku Co., Ltd., "KAYARAD" sold by Nippon Kayaku Co., Ltd., "Cylor cure" sold by Union Carbide Co., Ltd., and San Afro Co., Ltd., respectively. Photoacid generator "CPI", Midori Kagaku Co., Ltd. MADE generator "TAZ", "BBI", "DTS", "ADEKA OPTOMER" sold by ADEKA. And RHODORSIL sold by Rhodia.

The compounding quantity of a photocationic polymerization initiator is 0.5-20 weight part normally with respect to 100 weight part of total amounts of a photocurable adhesive composition, Preferably it is 1-15 weight part. When the quantity is less than 0.5 weight part, hardening may become inadequate and the mechanical strength and adhesive strength of an adhesive bond layer may fall. Moreover, when the amount exceeds 20 weight part, the hygroscopicity of an adhesive bond layer will become high by increasing the ionic substance in an adhesive bond layer, and the durability of the polarizing plate 20 obtained may fall.

The photocurable adhesive composition may contain a photosensitizer as needed. By using a photosensitizer, reactivity is improved and the mechanical strength and adhesive strength of an adhesive bond layer can be improved further. As a photosensitizer, a carbonyl compound, an organic sulfur compound, a persulfide, a redox type compound, an azo compound, a diazo compound, a halogen compound, a photoreducing dye etc. are mentioned, for example.

Examples of the carbonyl compound which may be a photosensitizer include benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, and α, α-dimethoxy-α-phenylacetophenone;

Anthracene compounds such as 9,10-dibutoxyanthracene;

Benzophenones such as benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, 4,4'-bis (dimethylamino) benzophenone and 4,4'-bis (diethylamino) benzophenone and their derivative;

Anthraquinone derivatives such as 2-chloroanthraquinone and 2-methylanthraquinone;

Acridon derivatives such as N-methylacridone and N-butylacridone;

acetophenone derivatives such as α, α-diethoxyacetophenone;

Xanthone derivatives;

Fluorenone derivatives and the like. Examples of organic sulfur compounds that can be photosensitizers include thioxanthone derivatives such as 2-chlorothioxanthone and 2-isopropylthioxanthone. In addition, a benzyl compound, a uranyl compound, etc. can also be used as a photosensitizer. These photosensitizers may be used independently, respectively and may use different multiple types together.

When mix | blending a photosensitizer, it is preferable to make the compounding quantity into the range of 0.1-20 weight part with respect to 100 weight part of total amounts of a photocurable adhesive composition.

Various additives can be mix | blended with the photocurable adhesive composition in the range which does not impair the effect. As an additive, an ion trap agent, antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow regulator, a plasticizer, an antifoamer, etc. are mentioned, for example.

Although the photocurable adhesive composition should just have a viscosity which can be coated by a suitable method to a film, it is preferable that the viscosity in 25 degreeC exists in the range of 10-30,000 mPa * sec, and 50-6,000 mPa * sec It is more preferable to exist in the range of. If the viscosity is less than 10 mPa sec, the apparatus which can be coated is limited and there exists a tendency for it to become difficult to obtain a homogeneous coating film without nonuniformity even if it can coat. On the other hand, when the viscosity exceeds 30,000 mPa sec, it will become difficult to flow, the apparatus which can be coated similarly will be limited, and it will become difficult to obtain a homogeneous coating film without nonuniformity. The viscosity here is a value measured at 60 rpm after temperature-controlling the composition at 25 degreeC using a Brookfield clay meter.

(5) pressure-sensitive adhesive layer (not shown)

An adhesive layer is a layer which has adhesiveness, and is used in order to bond the polarizing plate 20 to the liquid crystal cell 40. FIG. As an adhesive which forms an adhesive layer, what uses an acryl-type polymer, a silicone type polymer, polyester, polyurethane, a polyether, etc. as a base polymer is mentioned, for example. Among them, the acrylic pressure sensitive adhesive having an acrylic polymer as the base polymer is excellent in optical transparency, maintains proper wettability and cohesive force, and is excellent in weather resistance and heat resistance, and is excellent in heat and humidification. Since the problem of separate of hardly arises, it is used preferably.

In the acrylic base polymer which comprises an acrylic adhesive, the ester part has an acrylic acid alkyl ester which has a C20 or less alkyl group, such as a methyl group, an ethyl group, a butyl group, or 2-ethylhexyl group, (meth) acrylic acid, or (meth) acrylic acid Acrylic copolymers with a functional group-containing (meth) acrylic monomer such as 2-hydroxyethyl are preferably used. When the pressure-sensitive adhesive layer containing such an acrylic copolymer has any problem after bonding to the liquid crystal cell 40 and needs to be peeled off, the pressure-sensitive adhesive layer can be peeled relatively easily without generating peeling marks or the like on the glass substrate. have. It is preferable that the glass transition temperature is 25 degrees C or less, and, as for the acrylic copolymer used for an adhesive, it is more preferable that it is 0 degrees C or less. In addition, this acrylic copolymer has a weight average molecular weight of 100,000 or more normally.

As an adhesive which forms an adhesive layer, the diffused adhesive in which the light-diffusion agent was disperse | distributed can also be used. A light diffusing agent is for giving light diffusivity to an adhesive layer. The light diffusing agent may be fine particles having a refractive index different from that of the base polymer constituting the pressure-sensitive adhesive layer, and fine particles made of an inorganic compound or fine particles made of an organic compound (polymer) can be used. Since the base polymer which comprises the acryl-type base polymer mentioned above and the adhesive layer in many cases shows the refractive index around 1.4, what is necessary is just to select suitably from the thing whose refractive index is about 1-2. The difference in refractive index between the base polymer constituting the pressure-sensitive adhesive layer and the light diffusing agent is usually 0.01 or more, and is preferably 0.01 or more and 0.5 or less from the viewpoint of securing the brightness and visibility of the liquid crystal display device to which it is applied. It is preferable that the microparticles | fine-particles used as a light-diffusion agent are spherical, and also those close to monodispersion, and the microparticles whose average particle diameter is about 2-6 micrometers are used suitably.

As microparticles | fine-particles which consist of an inorganic compound, aluminum oxide (refractive index 1.76), silicon oxide (refractive index 1.45), etc. are mentioned, for example. Moreover, as microparticles | fine-particles which consist of an organic compound (polymer), for example, melamine resin beads (refractive index 1.57), polymethyl methacrylate beads (refractive index 1.49), methyl methacrylate / styrene copolymer resin beads (refractive index 1.50? 1.59) ), Polycarbonate beads (refractive index 1.55), polyethylene beads (refractive index 1.53), polystyrene beads (refractive index 1.6), polyvinyl chloride beads (refractive index 1.46), silicone resin beads (refractive index 1.46), and the like.

Although the compounding quantity of a light-diffusion agent is suitably determined in consideration of the haze value required for the adhesive layer in which it is disperse | distributed, the brightness of the liquid crystal display device to which it is applied, etc., it is normally with respect to 100 weight part of base polymers which comprise an adhesive layer. It is about 3-30 weight part.

The haze value measured according to JIS K 7361 of the pressure-sensitive adhesive layer in which the light diffusing agent is dispersed is 20 to 80% from the viewpoint of securing the brightness of the liquid crystal display device to be applied and making it difficult to cause blurring or blur on the display. It is preferable to set it as the range.

Each component (base polymer, light diffusing agent, crosslinking agent, etc.) constituting the transparent adhesive or the diffusion adhesive is dissolved in a suitable solvent such as ethyl acetate to form an adhesive composition. However, the components which are insoluble in a solvent such as a light diffusing agent are in a dispersed state. An adhesive layer can be formed by apply | coating this adhesive composition on the transparent resin film 23 and a release film (not shown), and drying it.

It is preferable that an adhesive layer has antistatic property in order to discharge static electricity which charges to the polarizing plate 20. The polarizing plate 20 may apply static electricity when peeling the release film laminated | stacked on the adhesive layer and bonding to the liquid crystal cell 40 etc. At this time, when the pressure-sensitive adhesive layer has antistatic property, the static electricity is quickly discharged, and the display circuit of the liquid crystal cell 40 is broken or the liquid crystal molecules are disturbed from being disturbed.

As a method of providing antistatic property to an adhesive layer, For example, the adhesive composition contains the metal microparticles | fine-particles, metal oxide microparticles | fine-particles, the microparticles | fine-particles which coated metal, etc .;

A method of containing an ion conductive composition comprising an electrolyte salt and an organopolysiloxane;

The method of mix | blending an organic salt type antistatic agent, etc. are mentioned. The antistatic holding time required is about 6 months at least from the viewpoint of the manufacturing, distribution, and storage period of a general polarizing plate.

In order to harden an adhesive bond layer, an adhesive layer may make active energy ray pass. Therefore, it is preferable to have a high transmittance in the spectral region of an active energy ray. Moreover, it is preferable that the characteristic as an adhesive does not change by irradiation of an active energy ray.

The pressure-sensitive adhesive layer is aged for about 3 to 20 days in an environment having a temperature of 23 ° C. and a relative humidity of 65%, for example, and then sufficiently bonded to the liquid crystal cell 40 after the reaction of the crosslinking agent is sufficiently advanced.

Although the thickness of an adhesive layer is suitably determined according to the adhesive force etc., it is about 1-40 micrometers normally. In order to obtain the thin polarizing plate 20 without impairing properties such as workability and durability, the thickness of the pressure-sensitive adhesive layer is preferably about 3 to 25 µm. In addition, when using the adhesive layer in which the light-diffusion agent was disperse | distributed, when the thickness of an adhesive layer is this range, the brightness | luminance in the case where the liquid crystal display device is seen from the front or obliquely is maintained, and the bleeding and blur on a display generate | occur | produce. It can be difficult.

(6) Protect film (not shown)

A protective film can be laminated | stacked on the surface on the opposite side to the surface bonded to the polarizing film 21 among the acrylic resin films 25. FIG. A protect film is a peelable film and is a member for protecting the surface of the acrylic resin film 25 from damage, abrasion, and the like. A protective film is comprised by the base film which consists of transparent resin, for example, and the adhesive layer which has the weak adhesiveness laminated | stacked on the surface of this base film. The protective film is bonded to the acrylic resin film 25 until the use of the polarizing plate 20, and is peeled off from the acrylic resin film 25 at the time of use.

A protective film can be obtained easily as a commercial item. Examples of commercially available products include "MASTAC" sold by Fujimori Co., Ltd., "Sunnytect" sold by Suneikaken, and Nitto Denko Co., Ltd. There are "E-MASK" and "TORETEC" sold by Torrefilm Kako Corporation.

(6-1) base film

A base film will not be specifically limited if it consists of transparent resin. As such a transparent resin, the acrylic resin represented by polymethyl methacrylate, the olefin resin represented by polypropylene or polyethylene, the polyester resin represented by polybutylene terephthalate or polyethylene terephthalate, etc. are mentioned, for example. Can be. In particular, polyethylene terephthalate is preferable because it is excellent in transparency and homogeneity, and also has a strong elasticity and low cost.

Moreover, a nucleating agent may be mix | blended with a base film in order to raise rigidity and to strengthen elasticity. A nucleating agent is a substance which becomes a nucleus of a crystal in a polymer molecule, and it has an effect which raises the crystallinity of a polymer and raises the elasticity modulus of a base film by mix | blending with a base film. As the nucleating agent, both an inorganic nucleating agent or an organic nucleating agent can be used. As an inorganic nucleating agent, talc, clay, calcium carbonate, etc. are mentioned, for example. As the organic nucleating agent, for example, metal salts such as metal salts of aromatic carbonic acid and metal salts of aromatic phosphoric acid, high density polyethylene, poly-3-methylbutene-1, polycyclopentene, polyvinylcyclohexane, etc. And a high molecular compound. Among these, an organic type nucleating agent is preferable, More preferably, they are said metal salts and high density polyethylene. Moreover, 0.01-3 weight% is preferable and, as for content of the nucleating agent in a base film, 0.05-1.5 weight% is more preferable. A nucleating agent may use only 1 type, and may use multiple types together.

It is preferable that the thickness of a base film is 15-75 micrometers. When this thickness is less than 15 micrometers, handling property may fall or the surface protection performance originally calculated | required may fall. On the other hand, when this thickness exceeds 75 micrometers, rigidity may be too strong, and also handleability may fall or peeling strength may become high.

It is preferable that it is 1,000 Mpa or more, and, as for the tensile elasticity modulus of a base film, it is more preferable that it is 3,000 Mpa or more. When this tensile elasticity modulus is too small, handleability may fall or it may become unbearable for the tension at the time of joining to the acrylic resin film 25. FIG. In addition, the surface of the base film may be subjected to antifouling treatment, antireflection treatment, hard coating treatment, antistatic treatment, or the like.

(6-2) pressure-sensitive adhesive layer

As an adhesive layer, well-known adhesive for re-peeling, such as an acrylic adhesive, can be used. Among them, acrylic resins having high elastic modulus and rigidity are preferable from the viewpoint of the elasticity of the protective film. In addition, from the point of elasticity, the thickness of an adhesive layer should be thicker. The pressure-sensitive adhesive layer may contain an antistatic agent or the like because no static electricity is generated during peeling.

As an acrylic adhesive, what consists of polymers which are based on 1 type (s) or 2 or more types of acrylic esters, such as butyl acrylate, ethyl acrylate, isooctyl acrylate, and 2-ethylhexyl acrylate, and which copolymerized a polar monomer to this is mentioned. . As a polar monomer, it is (meth) acrylic acid, 2-hydroxyethyl (meth) acrylic acid, 2-hydroxypropyl (meth) acrylic acid, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, for example. And monomers having a carboxyl group, a hydroxyl group, an amino group, an epoxy group, and the like, such as glycidyl (meth) acrylate. Moreover, crosslinking agents, such as a polyisocyanate compound, an epoxy compound, and an aziridine compound, may be mix | blended with an adhesive.

Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the following examples, parts showing the amount of use are based on weight unless otherwise specified. In addition, the measurement of the physical-property value in each example was performed with the following method.

[Measurement of curl amount of film]

First, according to the method according to the description performed with reference to FIG. 4, for each of the acrylic resin film, the polarizing plate, and the polarizing plate with the pressure-sensitive adhesive layer (the state with the peeling film and the peeling film peeled off) to which the protective film was attached, the film was Curled amount was measured with the convex side facing down. The case where the acrylic resin film side becomes convex is called reverse curl, and the case where it becomes concave is called normal curl.

[Measurement of Tensile Modulus of Film]

The tensile modulus of the film is a method defined in JIS KK7161 "Test Method for Plastic-Tensile Properties Part 1: General", using an autograph (model "AG-1", Shimadzu Corporation). It measured on the conditions of 22 degreeC of temperature, and 53% of a relative humidity.

Example 1

(a) Production of acrylic resin film

(Acrylic resin and acrylic elastomer particle)

The copolymer of the weight ratio 96/4 of methyl methacrylate / methyl acrylate was made into acrylic resin. In addition, the innermost layer contains a hard polymer that is a copolymer of methyl methacrylate and a small amount of allyl methacrylate, and the middle layer is a soft polymer that is a copolymer of butyl acrylate, styrene and a small amount of allyl methacrylate as a main component. An elastic body including an elastic body, the outermost layer comprising a hard polymer that is a copolymer of methyl methacrylate and a small amount of ethyl acrylate, and having a particle having an average particle diameter of 240 nm to the elastic body as an intermediate layer. It was used as acrylic elastomer particle.

(Production of Acrylic Resin Film)

The pellet in which said acrylic resin and said acrylic elastomer particle were mix | blended in the weight ratio of the former / latter = 70/30 was melt-kneaded with the twin screw extruder, and it was set as the pellet of an acrylic resin composition. This pellet was put into a single screw extruder having a diameter of 65 mm, extruded through a T-die at a set temperature of 275 ° C, and two polishing rolls having mirror surfaces set at both sides of the extruded film-like molten resin at a temperature of 45 ° C. It sandwiched and cooled between and produced the acrylic resin film.

(b) Bonding of protective film to acrylic resin film

A 60-micrometer-thick biaxially stretched polyethylene terephthalate film in which a weakly adhesive acrylic adhesive layer was formed on one side was prepared, and this was made into a protective film. This polyethylene terephthalate film had a tensile modulus of 3,500 MPa in the long direction (MD). The acrylic resin film and the protective film were bonded by the roll type lamination so that the pressure-sensitive adhesive layer of the protective film overlapped with the acrylic resin film. A 250 mm x 300 mm sample was cut out from the acrylic resin film (protect film adhesion acrylic resin film) to which the protective film was stuck, and the curl was measured. The curl value at this time was a minimum value of 7.0 mm, a maximum value of 31.0 mm, and was normal curl.

(c) Preparation of Polarizer

On one side of the polarizing film having iodine adsorbed on the polyvinyl alcohol film and polyvinyl alcohol and oriented, the acrylic resin film side of the protective film-adhesive acrylic resin film produced in the above (b) is on the other side of the polarizing film. 50-micrometer-thick "ZEONOR FILM" as biaxially oriented film of cyclic olefin resin (transparent resin film) obtained from Xeon Co., Ltd. (in-plane retardation value (R _o ) = 55 nm, thickness direction Phase difference value (R _th ) = 124 nm was bonded each, and the polarizing plate was produced.

In bonding, after apply | coating an ultraviolet curable adhesive composition as an adhesive agent to the bonding surface to each polarizing film of the said protective film adhesion acrylic resin film and a cyclic olefin resin film, and overlapping each coating surface on both surfaces of the said polarizing film, These films were integrated by passing through two bonding rolls 15 and 16. Here, the rubber roll whose surface was rubber | gum was used for the 1st bonding roll 15, and the metal roll in which chromium plating was performed on the surface was used for the 2nd bonding roll 16. As shown in FIG. In addition, of the first bonding roll 15, the peripheral velocity of the peripheral velocity (R ₂₎ of the second bonding roll 16 is disposed in the cyclic olefin based resin film side of the (R ₁₎ disposed on acrylic resin film side Ratio (ratio of main velocity) R <_2> / R <_1> was set to 1.0113. By setting the ratio of the circumferential speed in this manner, the shrinkage stress at the acrylic resin film side was larger than the shrinkage stress at the conveyance direction on the cyclic olefin resin film side.

In addition, in bonding, the tension | tensile_strength before bonding was provided to each of the said protective film adhesion acrylic resin film and cyclic olefin resin film in the direction along a conveyance direction (the longitudinal direction of a film), and was bonded to the polarizing film in this state. The tension before bonding was produced by the difference of the rotational speed of the feed roll which feeds out each film, and the winding roll which winds up the laminated polarizing plate. The measurement of the tension before joining was performed using the tension pickup provided before the joining roll. In addition, the cross-sectional area of each of the acrylic resin film and the cyclic olefin resin film was calculated, and the pre-bonding tension per unit area was calculated by removing the pre-bonding tension obtained above from the cross-sectional area. When the pre-bonding tension per unit cross-sectional area of the acrylic resin film is T ₁ and the pre-bonding tension per unit cross-sectional area of the cyclic olefin resin film is T ₂ , the pre-bonding tension per unit cross-sectional area of the cyclic olefin resin film (T The ratio (pre-bonding tension ratio) T ₁ / T ₂ of the pre-bonding tension (T ₁ ) per unit cross-sectional area of the acrylic resin film to ₂ ) was 0.94.

After bonding, using an ultraviolet irradiation device using a metal halide lamp as a light source, ultraviolet rays are irradiated from the cyclic olefin resin film side to cure an adhesive so that the amount of accumulated light at a wavelength of 320 to 400 nm is 200 mJ / cm 2, and the obtained adhesive is obtained. The polarizing plate was wound up to the roll.

(d) Curl | Karl evaluation of a polarizing plate

The 250 mm x 300 mm sample was cut out from the polarizing plate obtained by said (c), and left to stand at 25 degreeC for 1 hour. Then, the curl amount was measured by said method in the state which peeled off the protective film, and as a result, it was a reverse curl in which the cyclic olefin resin film side became concave, and was the maximum value -39.0 mm. This result is shown in Table 1.

[Example 2]

In Example 1 (c), the main speed ratio R ₂ / R ₁ was set to 1.0107, except that the polarizing plate was produced in the same manner as in Example 1. As a result of measuring the curl amount of the obtained polarizing plate by the method similar to (d), it was a reverse curl in which the cyclic olefin resin film side became concave, and was the maximum value -79.0 mm. This result is shown in Table 1.

Example 3

In Example 1 (c), the ratio of the tension before joining per unit cross-sectional area was 1.1, and it carried out similarly to Example 1 except having manufactured the polarizing plate. As a result of measuring the curl amount of the obtained polarizing plate by the method similar to (d), it was a reverse curl in which the cyclic olefin resin film side was concave, and it was the maximum value of -4.0 mm. This result is shown in Table 1.

Comparative Example 1

In Example 1 (c), the main speed ratio R ₂ / R ₁ was set to 1.0098, except that the polarizing plate was produced in the same manner as in Example 1. Under these conditions, the shrinkage stress at the acrylic resin film side is smaller than the shrinkage stress at the conveyance direction on the cyclic olefin resin film side. As a result of measuring the curl amount of the obtained polarizing plate by the method similar to (d), it was a reverse curl in which the cyclic olefin resin film side became concave, and was the maximum value -107.0 mm. This result is shown in Table 1.

Experiment Ratio of main speed Tensile ratio before splicing Curl (mm) Example 1 1.0113 0.94 -39.0 Example 2 1.0107 0.94 -79.0 Example 3 1.0113 1.10 -4.0 Comparative Example 1 1.0098 0.94 -107.0

(e) extrapolation of data

5 is a graph plotting the results obtained in Examples 1 and 2 and Comparative Example 1, which were tested at the same ratio of pre-bond tension. Negative (-) of the amount of curl indicates reverse curl, plus (+) indicates that it is static. As shown in this figure, there was a correlation between the circumferential speed ratio R ₂ / R ₁ and the curl amount, and it was found that the relationship between the two was in a linear (linear function) relationship. When the horizontal axis x is the main speed ratio and the vertical axis y is the curl amount, the regression line is expressed by the following equation (8). In addition, the correlation coefficient (R ² ) at this time was 0.99539.

y = 44211x-44754 Hz... (8)

Therefore, this regression straight line was extrapolated to find a range where the amount of curl is -80? +80 mm.

As a result, it was found that the main speed ratio R ₂ / R ₁ is in a range of 1.0105 to 1.0141. In other words, if the main speed ratio is within this range, it is considered that a polarizing plate in an appropriate range can be obtained particularly effectively, without the amount of curl excessive.

In addition, when Example 1 and Example 3 which were experimented with the same main speed ratio (1.0113) are compared, Example 3 whose ratio of the tension before joining per unit cross-sectional area is 1.10 implements that whose ratio is 0.94. It turns out that curl amount is considerably smaller than Example 1, and excessive reverse curl is suppressed. Therefore, it is preferable that the tension ratio before joining per unit cross-sectional area is 1.0 or more, More preferably, it is 1.1 or more like Example 3.

12: adhesive application device
13: adhesive application device
15: first bonding roll
16: second bonding roll
18: curing device
20: polarizer
21: polarizing film
23: transparent resin film
25: acrylic resin film
40: liquid crystal cell

Claims (7)

An acrylic resin film is bonded to one side of a polarizing film having a dichroic dye adsorbed to and oriented by a polyvinyl alcohol-based resin film and the polyvinyl alcohol-based resin film through an adhesive, and an adhesive on the other side of the polarizing film. As a method of manufacturing a polarizing plate by bonding a transparent resin film through
(A) The raw material film conveyance process which conveys the said polarizing film, the said acrylic resin film, and the said transparent resin film so that the said polarizing film may be sandwiched between the said acrylic resin film and the said transparent resin film,
(B) The said acrylic resin film is laminated | stacked on the single side | surface of the said polarizing film, and the said transparent resin film is laminated | stacked on the other surface of the said polarizing film via curable adhesive, respectively, and it contacts with the said acrylic resin film and conveys the said acrylic resin film Between the laminated body of the said acrylic resin film / the said polarizing film / the said transparent resin film with the 1st bonding roll which rotates in the direction, and the 2nd bonding roll which contacts the said transparent resin film and rotates in the conveyance direction of the said transparent resin film. A bonding step of bonding the acrylic resin film and the transparent resin film to the polarizing film by inserting in the
(C) after the said bonding process (B), hardening | curing the said adhesive agent, and providing the hardening process which adhere | attaches the said acrylic resin film and the said transparent resin film with the said polarizing film,
In the said bonding process (B), the shrinkage stress in the said conveyance direction in the said acrylic resin film side of the said laminated body rather than the shrinkage stress in the said conveyance direction in the said transparent resin film side of the said laminated body The manufacturing method of the polarizing plate by which the said transparent resin film and the said acrylic resin film are bonded by the said polarizing film in the state which tension was given to the said transparent resin film and the said acrylic resin film so that it might become large. The method of claim 1,
The said bonding process (B) is a manufacturing method of the polarizing plate performed so that ratio of the circumferential speed of the said 2nd bonding roll with respect to the circumferential speed of the said 1st bonding roll may be 1.0105 or more and 1.0141 or less. The method according to claim 1 or 2,
The bonding step (B) is a ratio of the tension per unit cross-sectional area of the acrylic resin film before bonding to the polarizing film to the tension per unit cross-sectional area of the transparent resin film before bonding to the polarizing film is one or more. The manufacturing method of the polarizing plate performed so that it may be carried out. 4. The method according to any one of claims 1 to 3,
The manufacturing method of the polarizing plate further equipped with the protective film bonding process of bonding a protective film to the surface on the opposite side to the surface bonded to the said polarizing film among the said acrylic resin films. 5. The method according to any one of claims 1 to 4,
The said transparent resin film is a film which is not extended | stretched, or the manufacturing method of the polarizing plate which is a film uniaxially or biaxially stretched. The method according to any one of claims 1 to 5,
The adhesive agent which apply | coats the said adhesive agent to the surface bonded to the said polarizing film of the said acrylic resin film in the middle of the said raw material film conveyance process (A), and apply | coats the said adhesive agent to the surface bonded to the said polarizing film of the said transparent resin film The manufacturing method of the polarizing plate further equipped with a process. The method according to any one of claims 1 to 6,
The said adhesive agent contains an active energy ray hardening resin, The said hardening process (C) is a manufacturing method of the polarizing plate performed by hardening | curing the said active energy ray hardening resin by irradiation of an active energy ray.

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